Someone needs to ask the question: where are the backups?
*I have multiple copies on other drives, but I want to know how everyone else is using the magic backup.
what do you mean?
and drobo doesn’t backup anything - it redundantly protects data from single / dual drive failure
The magic back up. You know. Because the Drobo protects against one or two disk failures, (SDR/DDR, single disk redundancy/dual disk redundancy), it is safe to use as the main/only storage for my data.
I don’t believe it, but it must be on Drobo website somewhere.
No, absolutely not. It protects against one or two drives failing, but that is not backup. One failed filesystem will take everything with it. If you delete data, it’s gone. If a program accessing it has a bug, poof - data is gone. It’s nicely redundant, but only against one specific thing - hard drive failure.
Let me re-emphasize this as much as I possibly can - Drobo does not provide backup and you still need another backup system, whether that’s a separate backup drive, a second Drobo, or the cloud.
Now, as to how it protects against drive failure in the first place, the best way to think about it is like RAID-5 (although it’s a bit more custom and complex than that). Take the following binary example:
0 + 0 = 0
1 + 0 = 1
0 + 1 = 1
1 + 1 = 0 (well, "10" actually, but we're only dealing with single bits)
You can expand this pretty easily to several bits:
1 + 0 + 0 + 1 = 0 (1 + 1 = 0, then the other zeros added are still 0)So that’s basic binary arithmetic. Now think of a simple case of 5 x 2TB drive. Each drive can be thought of as a stream of bits - 16 trillion in the case of a 2TB drive. In the simplest case, you just perform the above arithmetic on each of those 16 trillion bits across each drive, and store the result on the last drive.
Now say you lose drive 3…
1 + 0 + ? + 1 = 0You can just reverse the math and determine the missing bit. Pop in a new drive, do a lot of math, and boom - all the bits are restored, good as new!
Things get more complex when you want to handle multi-disk redundancy, and you don’t necessarily store all of the “answers” (called parity bits) on the same drive. The Drobo is even more fun since it can handle different drive sizes, grow the drives, shrink them - it’s the “secret sauce”. But the basics come down to a whole bunch of binary math like the above.
nice info with explanation diamond
I treat it like any other disk drive that might fail at any time.
I don’t believe in magic, Santa Claus, The Tooth Fairy, or Hard Drive Recovery Elves 
santa isnt real? 
No Paul, your parents were scamming you. So is Drobo marketing
(Drobo marketing’s approach to this is way up there on my list of high tech nits, and I have many of those…)
(heh, i could never quite figure out why the breadcrumbs trail from mince pies always led back up to their bedroom - LOL) 
Well, ok, if you want to go there… if you spent a lot of time, late at night, hanging around outside your parent’s bedroom, then no wonder you have the problems you have now.
(It’s an idle Sunday… what can I say??? )
Paul’s dad was performing backups?
lol, hey leave my dad out of it, or i’ll have to mention something about yomoma (yoyoma) - just kidding
“Keep(ing) your data safe” != Backup
at least not in the Drobo world.
It’s more like wearing your seat belt when driving. You’re more likely to survive a crash. But it doesn’t make you invincible by any length.
A backup is like having a clone. Car crash, no problem, get a new car, bring in the clone, keep going like nothing happened.
Somebody wake me up when DRI is ready to clone me.
The way I differentiate backup from redundancy is simple:
“Backup? How far back can I go?”
Diamondsw, I love your explanation of RAID.